A display unit is an electronic device for displaying video on, e.g., a screen to a user. Video may comprise either still or moving images or a combination of both. The display unit may be arranged to receive a video signal representing a sequence of video frames and to display the frames of the sequence consecutively. A video frame may be defined as a still (unanimated or immobile) image to be displayed for a limited amount of time. The inverse of the duration of a frame is known as the frame rate. The frame rate may be measured in frames per second (fps). By choosing a sufficiently high frame rate, for instance, more than 20 fps, an impression of motion may be achieved.
The video signal representing the sequence of video frames may be generated by a display control unit. The display control unit may, for instance, be arranged to generate the video signal on the basis of image data in conjunction with image descriptors. For example, each frame may have associated with it a set of one or more images to be displayed simultaneously by the display unit and a set of image descriptors describing, e.g., a geometrical arrangement of the individual images on a screen or an overlay or superposition of the images on the screen, or both.